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Small choice

The approach with the partitioning of the system into a QM and a classical molecular mechanical (MM) part, thus usually termed hybrid QM/MM procedure, provides a reasonable reduction of the computational effort by restricting the time-consuming QM calculation of forces to the most relevant part of the liquid system. The main error sources in this approach are a too small choice of the QM region, an inadequate level of theory for the QM calculation, the choice of suitable potentials for the MM part of the system, and smooth transitions of particles between QM and MM region. In conventional QM/MM procedures, the whole system is first evaluated at MM level and then corrected by the QM data. This means that classical potential functions (with all their problems and difficulty of construction) are needed for all components of the system. A recently developed methodology can reduce the need for such potentials to the solvent only, as will be outlined below. [Pg.146]

Concerning the use of ATRP with MIPs, the major limitation for this technique in the context of MIP synthesis is the small choice of monomers with suitable functional groups. Typical monomers used for molecular imprinting such as methacrylic acid (MAA) are incompatible, as they inhibit the metal-ligand complex involved in ATRP. With other monomers like methacrylamide [59] and vinylpyridine [60] it is difficult to achieve high monomer conversion. Template molecules also often carry functional groups that may inhibit the catalyst. All this seems to make ATRP not the best choice for molecular imprinting. Nevertheless,... [Pg.12]

A decade of detailed investigation has yielded a solid mass of consistent data, but the more important mechanisms have as yet only reached the stage where a small choice remains. [Pg.153]

The important part of interviewing is listeningl (Figure N4-6) It is not the interviewer who should have the last word. However, listening usually starts with a question from the interviewer. You may be tempted to use closed questions questions on which the answer might be yes or no, or one out of a small choice, or questions where you force the interviewed to agree or not. However, you may then only get the answer to your question the interviewed may not go on. Closed questions can be useful to get simple facts such as the name of the interviewed, and you can use them to prod the interviewed person, but do not only use closed questions. [Pg.252]

Improvements in separation by distillation have reached the stage of being restricted to improvements in liquid/vapour contacting equipment. The application of azeotropic distillation is restricted by the comparatively small choice of effective entrain-ers and the equipment required is very similar to that needed for fractional distillation so there are few possible applications that have not been fully explored. [Pg.159]

The obvious difficulty is the small choice of the appropriate elements to... [Pg.320]

Another approach to form a lens directly in the substrate material is to form first a lens in photoresist deposited onto the substrate using some of the above procedures. After that reactive-ion etching (fast, but relatively small choice of materials) or ion milling (slower, more materials) is used to transfer lens into the substrate... [Pg.53]

Phosphate fibers were to be a product of a company that at one time in the past had manufactured saccharine, NTA, and traces of dioxin as a byproduct in Agent Orange. These three products are background and help to explain some decisions made by management in the Phosphate Fibers Project. We were also a manufacturer of phosphates for detergents. You can understand that our management had but small choice to move very slowly and deliberately with the Phosphate Fibers Project irrespective of the benefit to humanity. History had taught us that even the noblest of efforts can be turned sour for the providers. [Pg.200]

The non-hydrocarbon components of crude oil may be small in volume percent, typically less than 1 %, but their influence on the product quality and the processing requirements can be considerable. It is therefore important to identify the presence of these components as early as possible, and certainly before the field development planning stage, to enable the appropriate choice of processing facilities and materials of construction to be made. [Pg.93]

The bare foot completion, which leaves an open hole section below the previous casing, is cheap, simple and suitable for consolidated formations which have little tendency to collapse. The slotted liner s an uncemented section of casing with small intermittent slots cut along its length, which prevents the hole from collapsing, but allows no selectivity of the interval which will be produced. The cased and cemented horizontal completion does allow a choice of which intervals will be perforated and produced. None of these examples provides any effective sand exclusion it this is required a gravel pack or a pre-packed liner can be used. [Pg.229]

In contrast to a direct injection of dc or ac currents in the sample to be tested, the induction of eddy currents by an external excitation coil generates a locally limited current distribution. Since no electrical connection to the sample is required, eddy current NDE is easier to use from a practical point of view, however, the choice of the optimum measurement parameters, like e.g. the excitation frequency, is more critical. Furthermore, the calculation of the current flow in the sample from the measured field distribution tends to be more difficult than in case of a direct current injection. A homogenous field distribution produced by e.g. direct current injection or a sheet inducer [1] allows one to estimate more easily the defect geometry. However, for the detection of technically relevant cracks, these methods do not seem to be easily applicable and sensitive enough, especially in the case of deep lying and small cracks. [Pg.255]

Metal-ceramic technology would be -if price problems were neglected- the better choice for a variety of small-power X-ray applications. The problem is that an universal X-ray tube is not (and probably will never be) available. [Pg.535]

Firstly, this is the supplying of energy needed for retaining the necessary volume of the liquid. Secondly, this is the choice of magnetic field topography in which the variation of meniscus position is small enough for different liquid quantities. [Pg.877]

Marmur [12] has presented a guide to the appropriate choice of approximate solution to the Poisson-Boltzmann equation (Eq. V-5) for planar surfaces in an asymmetrical electrolyte. The solution to the Poisson-Boltzmann equation around a spherical charged particle is very important to colloid science. Explicit solutions cannot be obtained but there are extensive tabulations, known as the LOW tables [13]. For small values of o, an approximate equation is [9, 14]... [Pg.174]

Truncation at the first-order temi is justified when the higher-order tenns can be neglected. Wlien pe higher-order tenns small. One choice exploits the fact that a, which is the mean value of the perturbation over the reference system, provides a strict upper bound for the free energy. This is the basis of a variational approach [78, 79] in which the reference system is approximated as hard spheres, whose diameters are chosen to minimize the upper bound for the free energy. The diameter depends on the temperature as well as the density. The method was applied successfiilly to Lennard-Jones fluids, and a small correction for the softness of the repulsive part of the interaction, which differs from hard spheres, was added to improve the results. [Pg.508]

In all of these stmctures the atomic positions are fixed by the space group syimnetry and it is only necessary to detennine which of a small set of choices of positions best fits the data. According to the theory of space groups, all stmctures composed of identical unit cells repeated hi three dimensions must confomi to one of 230 groups tliat are fomied by coinbinmg one of 14 distinct Bmvais lattices with other syimnetry operations. [Pg.1372]

Equilibrium constants for protein-small molecule association usually are easily measured with good accuracy it is normal for standard free energies to be known to within 0.5 kcal/mol. Standard conditions define temperature, pressure and unit concentration of each of the three reacting species. It is to be expected that the standard free energy difference depends on temperature, pressure and solvent composition AA°a also depends on an arbitrary choice of standard unit concentrations. [Pg.130]

Since 5 is a function of all the intermediate coordinates, a large scale optimization problem is to be expected. For illustration purposes consider a molecular system of 100 degrees of freedom. To account for 1000 time points we need to optimize 5 as a function of 100,000 independent variables ( ). As a result, the use of a large time step is not only a computational benefit but is also a necessity for the proposed approach. The use of a small time step to obtain a trajectory with accuracy comparable to that of Molecular Dynamics is not practical for systems with more than a few degrees of freedom. Fbr small time steps, ordinary solution of classical trajectories is the method of choice. [Pg.270]

Another option is a q,p) = p and b q,p) = VU q). This guarantees that we are discretizing a pure index-2 DAE for which A is well-defined. But for this choice we observed severe difficulties with Newton s method, where a step-size smaller even than what is required by explicit methods is needed to obtain convergence. In fact, it can be shown that when the linear harmonic oscillator is cast into such a projected DAE, the linearized problem can easily become unstable for k > . Another way is to check the conditions of the Newton-Kantorovich Theorem, which guarantees convergence of the Newton method. These conditions are also found to be satisfied only for a very small step size k, if is small. [Pg.285]

Thus, the time-dependent BO model describes the adiabatic limit of QCMD. If QCMD is a valid approximation of full QD for sufficiently small e, the BO model has to be the adiabatic limit of QD itself. Exactly this question has been addressed in different mathematical approaches, [8], [13], and [18]. We will follow Hagedorn [13] whose results are based on the product state assumption Eq. (2) for the initial state with a special choice concerning the dependence of 4> on e ... [Pg.387]


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See also in sourсe #XX -- [ Pg.34 , Pg.97 , Pg.98 , Pg.99 , Pg.100 , Pg.101 ]




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